1. Field of the Invention
The present invention relates generally to inertia type decelerometers and, more particularly, to microprocessor based inertia type decelerometers which make use of sensor means for detecting and measuring acceleration and deceleration of a vehicle in dual direction applications.
2. Description of the Related Art
In the related art, decelerometers utilize a mercury filled glass tube as a deceleration sensing device. The mercury filled glass tube is fragile and frequently broken, thereby releasing the hazardous fluid. Decelerometers of this mercury filled glass tube type only provide a closed switch indication of deceleration. In dual direction applications, two devices are required.
In the railroad industry in particular, microprocessor cab signal equipment has been using a mercury tube decelerometer to indicate pre-set brake rates. Two devices per railroad vehicle or locomotive are required--one for each direction of motion that is traveled along a railroad track. The principle of operation of the mercury tube decelerometer is that the mercury, due to its inertia, is caused to move within the confines of the glass tube when under the influence of deceleration. When the deceleration rate is sufficiently high, the mercury comes in contact with two electrical contacts in the glass tube and then an electrical circuit is completed, thereby sending a control signal to the system logic. In this manner, the mercury functions as a switch that closes at a predetermined deceleration rate. As a result, the decelerometer provides only a single rate of acceleration or deceleration depending upon when the mercury functioned as a switch that closed the two electrical contacts within the glass tube.